A protocol state of a communication channel between a network and a communication terminal, such as, but not limited to, a radio resource control (RRC) state of a communication channel, may significantly affect the energy consumption of the communication terminal as well as the load on the telecommunication system (notably in terms of radio resource usage, such as channel occupancy and therefore overall available bandwidth for all users). Indeed, each state may be associated with different procedures, rates of exchange of signalling information with the network, etc.
For example, in a system operating according to a High Speed Packet Access (HSPA) protocol, a channel may be in a RRC idle mode or in a RRC connected mode. In RRC idle mode, the user equipment (UE) is attached to the network but no data transfer occur. The RRC idle mode may be regarded as a channel state. In RRC connected mode, the channel may for example be in a CELL_DCH state (dedicated channel allocated for data transfer), a CELL_FACH state (common channel carrying the data), a CELL_PCH state (the UE can be paged, but must be switched to the CELL_FACH state for uplink data transfer) or a URA_PCH state. The meaning of these RRC states is known in the art and will not be repeated here. It suffices to mention that the power consumption associated with staying on these RRC states may significantly differ from each other. Typically, the power consumption of a UE in CELL_DCH state is approximately twice its consumption in CELL_FACH state and may be about fifty or a hundred times its consumption in CELL_PCH or URA_PCH state.
In fact, one reason for having originally introduced different channel states is to reduce the energy consumption of the UE. On the other hand, switching between channel states involves signalling, is thus also costly in terms of power consumption, and should consequently only occur when necessary and appropriate, i.e. when it is worth doing so. A trade-off needs to be found in that respect. The need for efficient channel switching procedures is particularly acute for packet-switched applications, such as for example TCP/IP-based applications. Indeed, although packet-switched applications may need to be “always-on”, they in reality usually involve bursty, intermittent data transfers, rather than a continuous data transfer. The volume of packet traffic, mostly IP traffic, significantly increased in recent years with the introduction of smartphones and the like in the mobile network, and is still increasing as of today.
International application WO 99/66748, hereinafter referred to as reference [1], relates to a mobile communications system wherein one or more traffic parameters are determined for a connection (established between a mobile station and a radio access network), and then the traffic parameters are used to predict a future value of that parameter(s). The state of a connection is then changed to another state based the predicted parameter value or values. A traffic parameter used for prediction is the amount of data in queue for the connection (reference [1], page 11, lines 9-11). The time interval between packets (of a bursty flow of packets) may be used as parameter to decide what type of radio channel to use to bear the packet data connection (reference [1], page 4, lines 8-10 and 14-15). For example, reference [1], page 16, line 27 to page 17, line 3 discloses: “After a last amount of data to be sent is transmitted, (e. g., the transmit queue is empty), a predefined time period is monitored. If a new data packet is not received at the end of that predetermined time period, then the dedicated channel is released, and a new shared channel is allocated to the connection”.
It is desirable to improve existing telecommunication systems involving channel state switching to further reduce the power consumption of communication terminals and to optimize radio resource usage, without increasing, or at least without excessively increasing, the implementation and architecture complexity and the associated equipment costs.